The first ionisation potential is maximum for

Options

A. V
B. Ti
C. Cr
D. Mn

Answer

To determine which element has the maximum first ionization potential among the given options (which are likely elements from the 4th period of the periodic table), we can analyze the trends in ionization energy across the period, particularly focusing on the 3d transition metals.

### Step-by-Step Solution:

1. **Identify the Elements**: The elements in the 4th period include:
- Scandium (Sc)
- Titanium (Ti)
- Vanadium (V)
- Chromium (Cr)
- Manganese (Mn)

2. **Understand Ionization Energy Trend**: Ionization energy generally increases across a period due to the increase in effective nuclear charge (Z_eff), which pulls the electrons closer to the nucleus, making them harder to remove.

3. **Consider Atomic Size**: As we move from left to right across the period, the atomic size decreases. A smaller atomic size leads to higher ionization energy because the outer electrons are held more tightly by the nucleus.

4. **Evaluate Electron Configuration**:
- Sc: [Ar] 3d¹ 4s²
- Ti: [Ar] 3d² 4s²
- V: [Ar] 3d³ 4s²
- Cr: [Ar] 3d⁵ 4s¹ (has a half-filled d subshell, which is stable)
- Mn: [Ar] 3d⁵ 4s² (also has a half-filled d subshell)

5. **Stability of Electron Configurations**:
- Chromium (Cr) has a unique electron configuration that provides stability due to its half-filled d subshell (3d⁵).
- Manganese (Mn) also has a half-filled d subshell but has two electrons in the 4s subshell.

6. **Comparing Ionization Energies**:
- Generally, half-filled and fully filled subshells are more stable and require more energy to remove an electron.
- Manganese, with a configuration of 3d⁵ 4s², is more stable than titanium and vanadium, which have incomplete d subshells.

7. **Conclusion**: Manganese, with its half-filled d subshell and higher effective nuclear charge compared to the other elements, will have the highest first ionization potential among the given options.

### Final Answer:
The first ionization potential is maximum for **Manganese (Mn)**.

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